Sorry if this has already been posted but, I have an 03 neon sxt. I am having problems with it getting hot. I have replaced Rad Cap, thermostat, and water pump, and I have tried to get any air out of system by running the heat and letting the car run. I put a funnel in my radiator and was looking for bubbles trying to get the air out of my system, and as long as I didn't turn on the a/c the bubbles went away, but if I turned on a/c it would be like a crazy boil going on, then I let cool down, and I took it for a drive without turning on a/c it never got over operating temp, and when I shut it off the temp gauge raised to the 3/4 mark, but if I go out and run the a/c it starts to run warm and when I shut it off and it gets real hot, almost In the red and the resivor starts boiling or sounds like its boiling, my bother in law thinks its the head gasket , but no water in oil and don't think there is water in coolent, looks kinda dark but thought it might just be old, no white smoke out of exhaust. So I really don't want to tear engine apart if its not gasket, what are your thoughts?

 

Is the radiator fan running when the a/c kicks in or when the car is hot? It also looks like the car is really getting hot and not a coolant temp. sensor problem right? Also, you replaced the w/p, rad cap, and thermostat. If it was me I would flush the system out really good in case there is rust or other blockage of the cooling system or radiator fins(Radiator and heating hoses ok?) To check for blown head gasket: milky film on oil filler cap, dip stick, or rockers. If you know someone with an exhaust analyzer they can sniff the coolant reservoir for fuel getting into the system.

 

Ok I went ahead and broke the engine down only to find the head gasket intack. You could not see a breech of any sort via head gasket, head, or block. Is it possible for head gasket to be bad and no evidence of it? And the head looked imaculent minus some carbon on valves, but on the top part it looks brand new. And come to think of it when I replaced the oil pan gasket there was no sludge or anything, looked like car only had 10000 miles on it. I was told to get the head checked and will be doing but everything just looks so good. I'm really lost

 

Yes fan comes on, and temp gauge acts correct, and I flushed the system took out thermostat and still ran hot, of course this was prior to me breaking it down....

 

Send the head to Machine shop and have them check for warp, crack, and have it serviced anyway.


Yes, plenty of case where you will find no evidence by looking at the gasket. especially when it is a steel head gasket.

 

Ok been thinking somemore, when I took everything apart there was now coolent anywhere, and if it were a warped head or cracked head wouldn't there be coolent somewhere? The only reasoning was to believe it was head gasket in first place was because with radiator cap removed the coolent bubbled. That was the only symptom... And note all the spark plugs looked the same, and the car only got hot when driving, if it was sitting still, not once would it get hot. I just really don't have the extra money to get head services if it is fine.

 

Geez, I think you checked everything and I'm at a lost on why it's overheating. I keep going back to the engine block and radiator fins. When you flushed the system did you disconnect the upper and lower radiator hoses from the radiator to make sure any rust will get blown out? Also, did you pull the radiator out and reverse flush it upside down?
I had a BMW that was overheating all the time. Radiator fins ran sideways instead of up and down. They were clogged and once I replaced it was fine.

 

Ok I went ahead and bought a new radiator, and got the new radiator, head, exhaust, and valve cover back on today. Tomorrow I will finish up. Then once I get it back together I will be jacking up the front end and making sure all the air is out of the system ( I heard that raising front end helps bleed coolent system). But what is throwing me is the head gasket showed no signs of any breech and when I took old radiator out the fins looked good and laying it down I put the water hose in it and it came out the otherside. I hope there could have still been something wrong with radiator. So tomorrow finish putting back together, along with new themorstat, and rad cap, bleed coolent system and keep my fingers crossed. Is there anything I'm missing guys? I know the cooling fans work cause I can see and hear them come on when it gets heated up, I know there is a heat sensor but I don't believe it is messed up cause the temp gauge reads accurate. Haven't replaced hoses, will probably pick them up tomorrow instead of putting old ones back on. But any other thoughts? Outside of cracked head but I really don't think it is, the head looked great, but if run hot again I'm going to do the hydrocarbon test. Will update tomorrow when do finished.

 

I feel bad that you are spending a lot of money trying to get the car cooled down. I love my 00 Neon and will fix what I can but I have to be realistic at 175,000 miles not to go too crazy fixing stuff. Well I hope for the best and that your car will be running like a champ soon. Good luck

 

Alright fellas the car is fixed!!!! ) I don't know which one it was ( radiator or head gasket) but I wish I would have changed radiator before getting into the engine. But I learned a lot seeing how this is the first engine I ever broke down and put back together. I'm very proud of myself, and look forward to many many miles on my car!!!